I am not aware of any prior art wherein a single sound-responsive element is combined with means to derive separate stereophonic "Right" and "Left" output signals from its displacements. A preliminary search has found the following U.S. patents:
(a) 2,173,994 Anderson PA1 (b) 3,534,181 Zimmerman PA1 (c) 3,666,896 Laue PA1 (d) 4,422,182 Kenjyo PA1 (e) 4,479,265 Muscatell.
Of this art, (a), (d), and (e) show monophonic microphones which employ optical sensing of the displacement of a diaphragm or the like. Items (b) and (c) show phonograph pickups which employ optical sensing of the displacements of the stylus.
The Anderson patent (a) of 1939 shows broadly a monophonic microphone using a mirror rocked angularly through a small arc by a linkage to a diaphragm, with photoelectric translating means. Kenjyo (d) shows a monophonic microphone wherein diaphragm displacement displaces a line or slit of light along a sensitive digital element. Muscatell (e) shows microphones having a loosely-suspended, low-mass, light-reflecting ball, e.g., 46 in FIGS. 7 and 8, responsive to sound waves; translation is by Doppler interferometry and is not stereophonic. Zimmerman (b) shows a stereo phonograph pickup with mirror 19 moved back and forth in its own plane by stylus 17. Translation into analog electrical signals is via the mirror and photosensors 6, 8. Laue (c) shows a stereophonic phonograph pickup with photoelectric translation. The stylus moves a "light screen" 55, his FIG. 5.